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Trees & Shrubs of the Eloise Butler Wildflower Garden

The oldest public wildflower garden in the United States

Kentucky Coffeetree

Common Name
Kentucky Coffeetree

 

Scientific Name
Gymnocladus dioicus (L.) K. Koch

 

Plant Family
Pea (Fabaceae)

Garden Location
Woodland

 

Prime Season
Spring flowering, seed pods in Autumn lasting to following spring.

 

 

Kentucky Coffeetree is a tall native deciduous tree, up to 80 feet high, with a narrow open crown.

Twigs are stout, light brown with white spots. Leaf scars are heart shape. Bud are hidden until leaf-out.

The bark of mature trees is a gray-brown and has a somewhat scaly appearance with sharp edges.

Leaves are large, alternate and bi-pinnately compound, 12 to 30 inches long, with up to six pairs of leaflets, each with numerous 1.5 to 2 inch ovate leaflets. This represents the largest leaves of any native North American species. No teeth on the leaflets, paler color on the underside. Yellow fall color.

Flowers: Kentucky Coffeetree is dioecious, that is, male and female flowers are on separate trees. In the late-spring appear the small, bluish-white, individually stalked flowers, arranged in a long terminal raceme, up to 6 inches long, and quite striking in color. The calyx is purplish with 5 narrow and long pointed teeth which shade to a whitish-green color. These teeth (the sepals) are almost as long and alternate with the 5 white petals which are wider and less pointed and broader near the tip. All these parts have fine hair. The stamens of the male flowers have yellow anthers and cluster in a pillar shaped group as tall as the petals are long. The receptacle of the female flowers is concave with a stout headed style. It too is as tall as the petals are long. The sepals and petals spread outward when the flower opens and do not resemble the typical pea family flower which usually has a banner petal, two laterals and two forming an enclosed keel.

The autumn fruit is a large (4 to 7 inch long, 1 to 2 inch wide) thick dark red-brown pod that usually stays on the tree over winter, but if it drops in autumn, it does not open at that time to disburse the seeds, but remains closed during the winter. The seeds are 3/4 inch bean-like rounded seeds, usually 4 per pod, but up to 6, that are embedded in a sticky pulp. Seeds in the spring can easily be germinated and planted but the seeds should be scarified first. Animals avoid the seeds and the leaves as they contain the toxic alkaloid cystisine.

 

Habitat: It is a superior tree for the home landscape as it is not known to be susceptible to disease or insects in this area. The Minnesota Landscape Arboretum introduced a cultivar in 1996 that is a male and is considered a superior shade tree. Full sun and moist soil is best for this tree.

Names: The generic name, Gymnocladus, is from two Greek words, gymnos, meaning 'naked' and klados, meaning 'a branch' and refers to the appearance of the tree when not in leaf - it appears to be dead when it is not in leaf, the buds do not swell until ready to leaf-out and it leafs out late and drops leaves early, providing many months of a 'dead-tree' look. The species name, dioicus, means 'of separate houses' and refers to the flowers being of a single sex on each tree. Other Gymnocladus species have bisexual flowers. The author names for the plant classification are as follows: First to classify was '(L.)' which refers to Carl Linnaeus (1707-1778), Swedish botanist and the developer of the binomial nomenclature of modern taxonomy. His work was amended by ‘K. Koch’ which refers to Karl Heinrich Emil Koch (1809-1879), German botanist, Professor of Botany, first professional horticultural officer in Germany, plant collector in and near Asia Minor. The common name comes from the seeds which were an early coffee substitute when roasted but are considered somewhat poisonous (as are the leaves) when not roasted. (Roasting neutralizes the toxin). More notes below.

See bottom of page for notes on the Garden's planting history, distribution in Minnesota and North America, lore and other references.

Kentucky coffeetree after leafdrop Kentucky coffeetree in summer Kentucky Coffeetree fall leaf color

Above: 1st photo - The pure form of a younger specimen of Kentucky Coffeetree, unconfined by other trees in early spring with the prior year's pods still attached; 2nd photo - in summer, in full leaf - 3rd photo - Fall leaf color.

Below: 1st photo - The stout twig with buds breaking and showing the typical whitish spots. 2nd photo - The flower raceme prior to flower opening. 3rd photo - The large twice compounded leaf.

Kentucky Coffeetree twig Kentucky Coffeetree flower bud Kentucky coffeetree leaf

Below: 1st photo - The bark of mature trees is furrowed and has a slightly scaly appearance. 2nd photo - A number of seed pods will persist overwinter on the tree and drop the next spring. As the tree leafs out late, this causes the tree to have a dead appearance in Spring.

Kentucky Coffeetree bark Kentucky Coffeetrtee old seed pods

Below: 1st photo - The male flowers opening on the large raceme. 2nd photo - The seed pod of the tree.

Kentucky coffeetree flower Kentucky Coffeetree seed pod

Below: 1st photo - A male flower. 2nd photo - A female flower. Note the petals of the flowers are broader and slightly longer than the sepals.

Male flower female flower

Below: 1st photo - The purplish calyx shades to greenish white at the tips of the long pointed sepals. 2nd photo - The 3/4 inch rounded seeds found in the pod.

calyx Kentucky Coffeetree seeds

Below: New seed pods formed by mid-summer are a yellow-green in color befor turning brown-black.

Kentucky Coffeetree green seed pod Kentucky Coffeetree seed pods

Below: One of the mature trees in the Eloise Butler Wildflower Garden, woodland garden. This specimen is a member of a grove of such trees. Drawing from Britton, N.L., and A. Brown. 1913. An illustrated flora of the northern United States, Canada and the British Possessions. 3 vols. Charles Scribner's Sons, New York.

Kentucky Coffeetree in the Garden drawing

Notes:

Notes: Kentucky Coffeetree first made it's appearance in the Garden in May 1909 when Eloise Butler planted some selections received from the Park Board. Martha Crone planted 36 small ones in 1934 that had been acquired the previous fall and heeled in for the winter. Additional plants came in 1949. A number of these still are growing in the Woodland Garden in the vicinity of Guidebook Station 10 and also along Violet Way. It is native to Minnesota in some south central counties and several counties in the SE near the Mississippi River. In North America it is found from the central plains states eastward, absent in NH, FL, VT and LA. In Canada it is only known in Ontario. In all places, wild populations in modern times are extremely rare.

Rarity: Wild populations were not found in Hennepin County where the Garden is located but it has been extensively planted in private and public landscapes. In the wild today in Minnesota it's habitat is becoming critical and the plant is now listed on the Minnesota DNR "Special Concern" list.

In 1975 in The Friends Newsletter, The Fringed Gentian™, Mr. Gordon Morrison, Coordinator of Environment Education for the Minneapolis Park Board wrote this:
“Over the last century the Park Board has planted a number of these interesting trees throughout the city. Most parks have at least one of them. The largest of these are two Kentucky Coffee­trees growing on either side of Minnehaha Creek just upstream from the point where Lake Nokomis flows into the creek. They are very slow growing here in the North. They may grow quite rapidly their first four or five years but then slow down to an almost unperceivable growth rate from then on. Those two near Lake Nokomis are only about one and a half feet in diameter though they are probably as much as seventy years old. Presumably those planted in the garden were planted many decades ago, perhaps by Miss Butler.”

Substitute for Coffee: It was not a good tasting beverage. Botanist Francois Michaux (Ref. #26b) wrote, in his North American Silva of 1819: "The name of Coffee Tree was given to this vegetable by the early emigrants to Kentucky and Tennessee, who hoped to find in its seeds a substitute for coffee; but the small number of persons who made the experiment abandoned it, as soon as it became easy to obtain from the seaports the coffee of the West Indies." He further writes: "The Coffee Tree was sent to France more than 50 years since. It thrives in the environs of Paris, where there are trees that exceed 40 feet in height, but it does not yield fruit, and is multiplied only be shoots obtained by digging trenches round the old trees. The divided roots produce shoots 2 or 4 feet long, the first year. The young trees are sought, on account of their beautiful foliage, for the embellishment of parks and pictoresque gardens."

References and site links

References: Plant characteristics are generally from sources 1A, 32, W2, W3, W7 & W8 plus others as specifically applied. Distribution principally from W1, W2 and 28C. Planting history generally from 1, 4 & 4a. Other sources by specific reference. See Reference List for details.

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